IMPACT MODIFICATION | MATERIALS
usage. Standard PP-based TPOs can be stiff and require improved flexibility and impact resistance in automotive interior trim and other applications. SBCs are often used because they have a unique molecular structure that helps them act as perfor- mance boosters for TPOs. They can enhance toughness at lower levels compared to traditional impact modifiers, resulting in favourable tough- ness/stiffness balance. “In our most recent study, we investigated the
synergistic use of SBCs in combination with POEs and how these modifiers influence TPO behaviour, while explaining the key benefits for the industry,” said Kristof Verschueren, senior Market Manager at Kraton Polymers, Belgium. “Hydrogenated SBCs have traditionally served as impact modifiers in TPO compounds. Kraton G1657 and G1730 are specifically designed for PP modification. Although POEs are increasingly used as alternative modifiers, SBCs remain valuable as secondary components in combination with POEs, enhancing the impact/ stiffness balance and improving melt flow.” The company carried out a study on talc-filled TPO compounds based on a high-flow PP homopolymer (100 MFR) matrix. Each formulation contained 15 wt.% talc and 25 wt.% impact modifiers, comprising a blend of POE and SBC, with SBC content varying from 0 to 5 wt.%. Results showed a three- to five-fold improvement in notched Charpy impact strength at both room temperature and -30° C when 5 wt.% SBC (G1657 or G1730) was incorporated, compared with formulations containing only POE. SBC addition also improved melt flow relative to POE-only formulations. The study also revealed that both G1657 and G1730 demonstrated synergy with low-density POEs, enabling optimised TPO performance for various industry applications and providing balanced performance/cost, said Kraton.
PLA modification PLA bio-based polymer was first introduced to consumers in food service ware and packaging because it was biodegradable in industrial com- posting facilities. However, the impact strength and heat tolerance of the material is quite low, making it inadequate for more demanding applications. There are many commercially available materials used as impact modifiers for PLA. TPU elastomers with both polyether and polyester soft segments are compatible, while olefin elastomers like polybutadiene, ethylene-propylene, and EPDM, can also be functionalised and blended with PLA. Using Green Dot’s Terratek Flex compostable elastomeric bioplastic in PLA has been shown to
PLA compounded with Terratek Flex at 10%, 20% and 30% Source: Green Dot Bioplastics
increase impact strength and flexibility while enhancing compostability, according to the company. Terratek Flex is a proprietary patent pending starch-based compostable elastomer verified by SGS Fresenius Laboratories to meet US (ASTM D6400) and EU (EN 13432-08) standards for biodegradability in industrial composting facilities. To study its use in detail, Green Dot compound-
ed PLA with Terratek Flex at 10%, 20%, and 30%, and sent the samples to an independent laboratory where they were moulded and tested using ASTM standards. Notched Izod Pendulum Impact tests showed an incremental increase in impact strength at the 10% and 20% levels with greater increases in impact strength achieved between the 20% and 30% levels. Impact strength increased from 0.549 ftlb/in in the 10% sample to 0.66 ftlb/in in the 20% sample, then jumped to 1.82 ftlb/in for the 30% loading level. Un-notched Izod tests showed comparable results. “From 0% to 20%, the increase is very linear,”
noted Green Dot’s Product Development Manager, Mike Parker. “After 20%, however, we see a much more exponential increase in the impact strength of both the notched and un-notched test results. This feature allows the engineer to customise the properties of the final resin and provides a certain degree of control to their cost to performance ratio.”
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.avient.com �
https://www.kuraray.eu �
https://eng.sk.com �
www.xeniamaterials.com �
www.elix-polymers.com �
www.ineos.com �
https://kraton.com �
www.greendotbioplastics.com
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